Thermostatic switch



Feb. 13, 1962 H. D. EPSTEIN 3,021,405

THERMOSTATIC SWITCH Filed Feb. 26, 1959 3,021,405 THERMOSTATIC SWITCH Henry David Epstein, Cambridge, Mass., assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware I Filed Feb. 26, 1959, Ser. No. 795,792 14 Claims. (Cl. 200-138) This invention relates to thermostatic switches and more particularly to thermostatic switches for insertion into small spaces such as in and about motor windings.

Briefly, the present invention provides an inexpensive small sealed thermostatic switch for protecting motor windings, and the like, comprising a container of two parts separated by an electrically nonconductive layer, and a thermostatic member in the container attached to one of the parts and positioned to close a circuit with the other part of the container.

Among the objects of the present invention are the provision of thermostatic switches useful for protecting motor windings; the provision of switches for this purpose which may be economically constructed and, if desired, sealed in connection with motor windings; the provision of such switches which are composed of a low number of parts which can be easily assembled; the provision of such switches which can beconveniently calibrated as a step in assembly; and the provision of switches of the type indicated which are small in size yet effective for the purpose intended. Other objects and features will he in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the construction hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIG. 1 is a much enlarged side elevation of a thermostatic switch made according to the present invention;

, FIG. 2 is a top plan of the thermostatic switch;

FIG. 3 is an axial section taken on line 3-3 on FIG. 4 is a cross section taken on line 44 on FIG. 2;

FIG. 5 is a plan view of the insulating element;

FIG. 6 is a view similar to FIG. 3 but exaggeratedly illustrating calibration of the device prior to completing its construction; and,

FIG. 7 is a fragmentary view similar to FIG. 3 but illustrating a different way of calibrating the device.

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2 be noted that thermostatic element 19 is attached to the terminal 9 of part 3 of the container and is therefore in conductive electrical engagement therewith. It is separated from part 5 of the container by insulator 13 except for the portion of the thermostatic element which projects i through opening to make and break electrical contact with part 5 through button 21 and conductive surface 23. The thermostatic switch ofthe present invention is conveniently assembled by applying a synthetic resin (epoxy resin for example) to both sides of insulator washer 13,

I placinglthe two parts of the container on either side thereof as shown in the drawing and then curing the epoxy resin. For this purpose a thermosetting epoxy resin is particularly desirable and this is allowed to cure and set in place after the parts of the switch have been assembled and calibrated. The parts are preferably further held together by wrapping a layer of fMylar film tape around the terminals 9 and 11 at the region 27. This not ,only renders the assembly more sturdy but facilitates holding the parts together during curing. The tape around area 27 is preferably also held in place with a thermosetting epoxy resin.

Becauseof the capsule shape of parts 3 and 5 when 1 assembled, the switch, may be conveniently calibrated during assembly by slidable adjustment of parts 3 and 5 on the adjacent substantially coplanar flange-forming portions (8, 12) and (10,14). FIG. 6 illustrates such a device aftercalib'ration effected by slidingly changing the relative position of parts 3 and 5. By sliding part 3 withrespect to part 5 before the resin is set, the tension .placed upon thermostatic member 19 is changed by the cam-like action of the sloping surface 23'relative to contact 21. j

FIG. 7 illustrates another way of calibrating the'switch either in lieu of or in addition to the method described above. By dimpling part 5 at the point 29, the point where contact 21 meets area 23, the tension placed upon thermostatic member 19 is also changed. If desired, calibration may be. effected by a combination of such .dimpling and slidable adjustment.

Because of the thermal conductivity of the metal parts 3 and 5, the thermostatic arm 19 is efliciently temperature responsive not only to resistance-induced heat caused by current passing through it, but also to the ambient Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now to the drawings, the thermostatic switch 1 of the present invention includes a container comprising two parts 3 and 5, both constructed of heat conductive material such as metal. The parts 3 and 5 areformed to form a hollow shell or capsule 7 and have projecting nonconductive material. Mylar polyester film is a suit able material for this purpose. Member 13 is formed with an opening 15 to accommodate the contact bearing end 17 of thermostatic member 19. Thermostatic member 19 conveniently carries a conventional contact button I 21 for engagement with the interior of part 5. Part 5 is coated with an electrical contactmaterial such as silver at the surface area 23 for this purpose.

While not restricted thereto, thermostatic element 19 is preferably made of bimetal and includes a dished portion 25 for imparting snap action to this element. It will temperature. The'switch accordingly functions effectively to protect motor windings when intersticially located in respect thereto. By connecting terminals 9 and 11 in the motor circuit, operation of the thermostatic switch will interrupt the current to the motor not only when the current reaches an undesired value but also when the motor windings become overheated for any veniently attached to both parts of the container by means of a separate adhesive, it may, if desired,.be pressure sensitive or composed of an adhesive material per se. Although the thermostatic member 19 is preferably snap acting, a creep acting thermostatic element may be employed, if desired.

Since the switch is sealed during manufacture it may be placed on a motor winding and the winding subsequently processed as by dipping and baking. Thus the switch and winding assembly may be dipped and balted as a unit without danger of the dipping compound penetrating into the switch. The switch of the present invention being a sealed device, can, therefore, be assembled into motors at the desired stage so as to become an inte ral part thereof.

From the foregoing, it will be clear that the switch of the present invention is constructed of only a few simple parts which may be easily assembled to form a device which can be calibrated during manufacture and remains protectively sealed during use. The switch is accordingly inexpensive to manufacture yet is efiective for the purpose intended.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A thermostatic switch comprising two conductive members shaped to form a hollow capsule when assembled, and providing line connections, an insulating member sandwiched between said members and attached thereto by means of a set synthetic resin to form a seal, said insulating member having an opening therethrough, and a snap-acting thermostatic member attached to one of said conductive members and supporting a contact engageable and disengageable interiorly with the other one of said conductive members, said thermostatic member extending operatively through said opening, each of said conductive members having a marginal flatflange means for engagement with said insulating member around said opening, whereby one conductive member shall have been slidable relative to the other on opposite sides of the insulating member prior to setting of said resin to adjust the relationship between said contact and said other conductive member, said other conductive member being provided with a portion extending toward and adjacent the contact on the thermostatic member, whereby through sliding prior to resin setting one of various possible contact pressures inheres at a given temperature after the resin has set.

2. A thermostatic switch according to claim 1, wherein said extending portion is constituted by a contact-formin sloping portion of said other conductive member.

3. A thermostatic switch according to claim 1, wherein said extending portion is constituted by a dimple in said other conductive member.

4. A thermostatic switch according to claim 1, wherein said capsule-forming conductive members include projecting ear-forming parts for making electrical connections.

5. A thermostatic switch according to claim 4, including a winding around said ear-forming parts.

6. A thermostatic switch comprising two assembled conductive members shaped to form when assembled a hollow capsule providing line connections, an insulating and sealing member sandwiched between said members and attached thereto by a cured synthetic resin, said insulating member having an opening therethrough, a thermostatic member conductively attached to one of said conductive members and supporting a contact engageable and disengageable interiorly with the other one of said conductive members, said thermostatic member extending through said opening, each of said conductive members being marginally provided with relatively slidable engaging flange means shaped for sealing engagement with said insulating member around said opening in all elative sealing positions of the flange means, whereby one conductive member shall have been slipped relative to the other during assembly with said sealing member and prior to curing of said resin to adjust the contact relationship betwee said contact and said other conductive member, said other conductive member being formed with an engageable contact surface adjacent said contact.

7. A thermostatic switch construction com rising two conductive members shaped when ass-cabled to form a hollow capsule providing line connections, an insulating and sealing member sandwiched between said members and attached thereto by a set synthetic resin, said insulating member having an opening therethrough, a thermostatic member conductively attached to one of said conductive members and supporting a contact engageeble and disengageable interiorly with the other one or" said conductive members, said thermostatic member extending through said opening, each of said conductive memb rs being provided marginally with substantially flat-flange means f r e gagement with said insulating member around said opening, whereby one conductive member is adapted to be slipped relative to the other during assembly with said sealing member and prior to setting of said resin to adjust the contact relationship between said contact and said other conductive member.

3. A thermostatic switch construction comprising two conductive members relatively slidable on a plane of slip and shaped when assembled to form a hollow capsule providing line connections, an insulating and sealing member sandwiched between said conductive members and attached thereto by a settable synthetic resin, said insulating member having an opening therethrough, a the mostatic member conductively attached to one of said conductive members and supporting a contact engageable and disengageable interiorly with the other one of said conductive members, said thermostatic member extending through aid opening, said other conductive member being formed with a sloping surface adjacent said contact, which surface slopes relative to the plane of slip, whereby desired contact pressure is obtained after setting of said resin.

9. A thermostatic switch construction comp; two conductive members shaped when assembled to form a switch body having line connections, a thermostatic member conductive.y attached to one of said conductive members and supporting a movable contact engageable and disengageable interiorly with the other one of said conductive members, an insulating member sandwiched between said members and attached thereto by an initially fiowable but finally set resin, said insulating member and said conductive members being shaped for relative movements of said conductive members on opposite sides of the insulating member when the resin is in flowable form, said insulating member form ng a passage for said thermostatic member, said thermostatic member extending across said insulating member at said passage, said other conductive member being formed with a fixed contact adjacent said movable contact.

10. A thermostatic switch comprising two conductive housing parts having adjacent rims and shaped to form a hollow capsule, sealing and holding means between the rims comprising an initially tiowable but finally set electrically insulating resin, a movable conductive thermostatic member in direct conductive contact with one of said conductive housing parts, the other conductive housing part being formed with a sloping surface, said thermostatic member having a movable portion carrying a contact engageable and disengageable with said. sloping surface of said other part, said parts being adapted for relative sliding movement when said resin is fiowable, whereby the contact pressure between said contact and said sloping surface may be varied when said resin is fiowable, said resin electrically insulating said conductive housing parts from each other.

11. A thermostatic switch according to claim 10, wherein the thermostatic member is of the snap-acting type, and wherein said sealing means includes a washer forming part of the sealing means and is held by said resin between 12. A thermostatic switch according to claim 11, where- V in portions of said rims and of said washer therebetween have extensions, the rim extensions sandwiching the wash er extensions, and including switch terminal portions projecting from the rim extensions.

13. A thermostatic switch comprising housing parts having adjacent rims and shaped to form a hollow capsule, sealing and holding means between the rims comprising an initially flowabie but finally set resin, a conductive thermostatic member in direct conductive contact with one of said conductive housing parts and having a movable portion carrying a contact engageable and disengageable with the other conductive housing part, said thermostatic member being of the snap-acting type, said two conductive rim extensions sandwiching the washer extensions, switch terminal portions projecting from the rim extensions, and

a mass of insulating materialsurrounding said rim and washer extensions, said washer and resin forming an electricallyinsulating barrier between said conductive housing parts. I

14. A thermostatic switch according toclaim 13, wherein said mass is constituted by a wrapping of insulating tape.

sealing means including a washer forming part of the seal- 7 References Cited in the file of this patent UNITED STATES PATENTS 1,901,775 Reichold Mar. 14, 1933 2,619,564 Raleigh NOV. 25, 1952 2,820,870 Mosku Jan. 21, 1958 2,878,343 Dales 'Mar. 17, 1959 2,916,586 Kuhn Dec. 8, 1959 2,937,250 Onksen et al. May 17, 1960 FOREIGN PATENTS 6,471 Great Britain Jan. 28, 1909 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, {021,405 February I3 1962 Henry David Epstein peers in the above numbered pat- It is hereby certified that error ap d Letters Patent should read as ent requiring correction and that the sai corrected below.

Column 4, line 63 strike out "having a movable portiorflo Signed and sealed this 5th day of June 1962.,

(SEAL) Attest:

DAVID L. LADD Commissioner of Patents ERNEST W. SWIDER Attesting Officer 

